Electrical illumination.



E. WEINTRAUB.

ELECTRICAL ILLUMINATION.

APPLICATION FILED FEB.9, 1907.

Patented Sept. 30, 1913.

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EZEGHIEL WEINTRAUB, OF SGHENECTADY, NEW" YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL ILLUMINATION.

Specification of Letters Patent. Patented Sept. 30, 1913.

Application filed February 9, 1907. Serial No. 356,541.

To all whom it may concern:

Be it known that I, EZECHIEL IVEIN- TRAUB, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electrical Illumination, of which the following is a specification.

My present invention relates to the production of light.

It comprises a new method of transforming electrical energy into light by heating a refractory body to incandescence through the medium of electrical energy passed through an attenuated vaporous medium.

It also comprises means whereby this result may be attained.

In accordance with the provisions of the statutes relating to patents, I have hereinafter described how my invention may be applied in practice, and I have illustrated one form of apparatus suitable for use in accordance with my invention. I do not, however, consider that my invention is limited to this particular form of apparatus, and in the claims appended hereto I have defined the scope of my invention as I understand it.

Before considering'in detail the fundamental principles underlying my invention, reference is made to; the accompanying drawings showing two formsof apparatus whereby my invention may be applied to the useful arts.

Figure 1 shows in section a vapor-electric device provided with a capillary tube according to my invention; Fig. 2 is a fragmentary view of a modified device in which therefractory tube is insulated from both electrodes.

Fig. 1 illustrates an evacuated envelop 1 of glass or other suitable material somewhat similar in form and proportions to the 7 envelops used with mercury vapor apparatus.

The envelop has a relatively large bulb or condensing chamben 2 atthe top, and into this projects a leading-in conductor 3 through which electrical energy may be introduced into the envelop. An electrode 4 of graphite or "other suitable material is connected to the lead wire 3 and cooperates with other elements in a manner hereinafter T described. The envelop is provided-with a second electrode 5 connected with a second the mercury electrode.

Tconditions, certain other materials have marked adv ltages, as hereinafter set forth. The external circuits of the device may consist of a conductor 7 connecting electrode 4: with one side of an electrical circuit,'say the positive side of. a direct current source, and a similar conductor 8 for the other electrode of the device. -A switch 9 and resistance 10 are connected in parallel with the device for use during the starting operation. A reactance 11 may be connected in series with the conductor 7, and a resistance 12 may be connected in series with conductor 8.

The various elements above described would constitute what might be termed, a mercury arc lamp, of which electrode I is the anode and electrode 5.the cathode. Such a lampcould be started on a direct current source by closing switch 9 to cause a current to flow in reactance 11, and then opening the circuit at switch .9 to allow reactance 11 to discharge at high potential across the gap between electrodes 4 and 5.

Such a high. potential discharge would serve to establish a conductive condition be- 'small annular space about the electrode.

The top of the tube is contracted to, form a close joint with the refractory bushilfg 1,5 which separates electrode 4 from the glass which inc-loses the leading-in conductor The joint between the bushing 15 and the constricted neck need not be vapor tight. Th lower end of the tube 13 is flared outward to form a cup 16 at the surface of Suitable stays or supports 17 fitted with refractory bushings 18 may be used to, hold tube 13 in position.

I have not specified the material of the best material available when the device is to high voltage.

tube as I contemplate the use of various materials differing radically in some of their properties.

Assuming, for purposes of illustration, that the element 18 is a porcelain tube with a bore ranging in diameter from 1/4 inch down to 1/64 inch or even less, the operation of the device is as follows :-An electromotive force of several hundred volts is impressed across conductors 7 and 8, but no current flowsbetween anodes 4 and 5 because of the non-conductive space which separates them. Switch 9 is then closed to store energy in 'reactance 11; it is subsequently opened to cause that reactance to discharge its energy at high potential between electrodes 4 and 5. This discharge will take place through the bore of the porcelain tube to the small electrode surface exposed within the cup 16 at the lower end of the tube. This discharge of energy serves to establish a conductive path between electrodes 4 and 5, and through this path a direct current is maintained by the voltage impressed on conductors 7 and 8. Under the conditions above set forth the current is in reality carried by a mercury arc inclosed by the porcelain tube 13. If the tube has a small bore, the arc will be of a very small cross-section and of relatively The current may be small, say in the neighborhood of a fraction of an ampere. I find that'if I continue to supply current to the are between the electrodes I can gradually heat up the porcelain tube to any desired temperature, even up to that at which the tube melts and goes to pieces.

From the above description it will be understood that the inclosed tube 13 may be raised to incandescence even though it is initially non-conductive, solely by the heating action of current passed through the vapor ous or gaseous medium in proximity to the material to be heated.

i I have above referred to a porcelain tube as it is one of the materials easy to form into a tube of small bore, and is a material the .properties of which are relatively well understood. Porcelain, however, is not the be used as a source of illumination Porcelain melts down at about 14COO centigrade. Tube 13 instead of being of porcelain, may be made of silica. As silica is transparent, the light delivered by the device is in this case a blended light containing rays from the incandescent silica and other rays from the mercury are within the tube.

The evacuated space outside the heated tube serves to prevent, in large measure, the dissipation of heat by conduction, so much so that I have succeeded in heating silica tubes to melting temperature with a current as small as one-half an ampere and an electromo'tivc force of about 100 volts. The

' silica tube in this case was approximately five inches long and had a bore of about 1/25 of an inch.

For improving the radiation capacity and securing the benefit of other advantageous properties, I may use a tube of refractory oXid such as thorium oxid or zirconium oxid.

Thorium oxid is well adapted for this use because of its stability at high temperatures. A thorium body has the further advantage that it possesses selective radiation. When the thorium oxid tube is used as shown in Fig. 1, the oxid is brought to incandescence by energy liberated by the mercury are; not by energy developed in' the thorium oxid itself .by the passage of current therethrough. I aim to keep all the electrical energy passing through the are, so that no electrolysis or other disintegrating action may take place in the thorium oxid. The thorium oxid is preferably as pure as possible and free from other rare earth oxids which might tend to increase the conductiv' ity and impair the refractory properties. In an apparatus of the type illustrated in the drawing, several factors tend to prevent the passage of current through the thorium oxid; The mercury 01' other vaporizable material of electrode 5 furnishes an eflicient source for the liberation of vapor, and'receives energy from the arc with a comparatively small voltage drop at the electrode surface There is therefore little'tendency for the arc to desert the metal and run to the oxid tube as cathode. Pure thorium oXid has a very high electrical resistance and even up to red heat, say 1400 centigrade, does not conduct appreciably. The resistance of themercury arc decreases somewhat as its temperature increases, thus tending to prevent the passage of current through the oxid.

I have pointed out the fact that the conductivity of the refractory tube is not relied on to maintain incandescence, but I do not consider that I am limitedto the use of non-conductive material for refractory tubes. I understand my invention to include refractory tubes of such material as boron, tungsten, and other high melting elements refractory enough to stand the high temperature and chemically inert with respect to the mercury or other vaporizable material used as cathode in the apparatus. In such cases, however, I consider it advisable to insulate or separate the refractory tube from one or both of the electrodes.

A modified form of device is illustrated by Fig. 2, in which the tube l3is insulated from the electrode by the refractory insu- I have mentioned the fact that the evacuated space surrounding the refractory tube prevents radiation of heat from the tube.

The onstant vaporization of mercury tends,

however, to increase this radiation. The heat insulation can be made more effective by the use of a cathode of amalgam or of zinc or some metal which does not vaporize as easily as mercury.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The process of electric lighting which consists in passing a mercury vapor are through a tube of very small bore consisting of refractory material in an exhausted space,

, and delivering sufiicient energy to said are to maintain the walls of said tube at incandescence'l 2. The method of maintaining a fine bore tube of refractory material, excessive in length with respect to its diameter, at incandescence which consists in passing a metal-- lic vapor are through its bore in an exhausted space, whereby a luminant of low current and high voltage characteristics is secured.

3. The process of converting electrical energy into light which consists in striking a high voltage,low current metallic vapor are through an evacuated space in a fine bore tube of refractory material excessive in length with respect to its diameter, whereby said material is heated to incandescence.

4. The combination of a mercury electrode, a' cooperating electrode, a highly re- 4 fractory tube of very fine bore interposed between said electrodes, an evacuated inclosing envelop and means for striking an are between said electrodes through the bore of said tube, thereby maintaining it at incandescence.

5. The combination of an exhausted envelo'p, electrodes therein, at least one of which consists of mercury, and a tube of highly refractory material having a diameter of about 1/4: to 1/64 of an inch, and means for striking an are through the bore of said tube thereby maintaining it at steady incandescence.

6. The combination of an exhausted envelop, electrodes therein, at least one of which consists of mercury, a tube of very small bore consisting of thorium 'oxid, and means for startin an are between said electrodes through said tube to heat the same to incandescence.

In witness whereof, I have hereunto set my hand this 7th day of February, 1907. 5

EZECHIEL WEINTRAUB.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

